The role of laparoscopy in gynecological and gyne-oncological surgery has dramatically increased over the past decades. Although laparoscopic procedure has several advantages over open surgery such as reduced blood loss, faster recovery earlier return to normal activities and work, however, postoperative pain and some hemodynamic changes sometimes discomforts the patients, lessening quality of life at postoperative period [1-3]. In clinical practice the majority of laparoscopic procedures are performed using standard pressure pneumoperitoneum (SPP, 12-15 mmHg) [1-3]. These noticeable adverse effects are associated with of creation of pneumoperitoneum with carbon dioxide (CO2) but it is requisite in all laparoscopic surgery for adequate visualization and operative manipulation.

The incidence of pain after gynecologic laparoscopies has been reported to vary from 35% to 63% [4,5]. A randomized controlled trial has demonstrated that there may be more intense pain and greater analgesia requirements in the immediate postoperative period after laparoscopic surgery than after laparotomy [6]. The origin of pain after laparoscopy is multifactorial and complex. It can be differentiated into abdominal pain and shoulder pain [7]. The precise causes for such pain are still obscure. Abdominal pain may be attributed to stretching of the abdominal cavity, and peritoneal irritation due to entrapment of dissolved CO2 [1-7]. Intraperitoneal acidosis, mucosal ischemia and compression of the splanchnic nerve as a consequence of the pneumoperitoneum may also be relevant factors [8,9]. On the other hand, shoulder pain is related to phrenic nerve and diaphragm irrigation due to residual CO2 in the subdiaphragmatic space [7-9].

In addition to pain, CO2 insufflation and a concomitant steep head-down (Trendelenburg, TP) position in surgical procedure also cause an increase in intra-abdominal pressure, which unfavorably affect patients homeostasis, inducing a significant change in the respiratory and cardiovascular system, lessening perfusion in abdominal organs and blood flow in the inferior vena cava, and posing an increased risk of thrombotic disease [10,11].

Low-pressure pneumoperitoneum (LPP, 7-10 mmHg) is recommended to minimize the adverse side effects associated with SPP [12]. There are several reports on the safety of low CO2 pneumoperitoneum pressure (LPP) in gynecological laparoscopic procedures however their trials have some limitations due to the small sample size, performed in only short laparoscopic procedures, and inadequate to assess the surgical impression of visualization [13-16]. Thus, further studies are still required.

Therefore, the purpose of this randomized controlled trial (RCT) is to assess the effect of LPP versus SPP on metabolic response, postoperative pain scores, surgical field visualization.

Inclusion Criteria:

• Women underwent a total laparoscopic hysterectomy with or without additional surgery, such as salpingo-oophorectomy, salpingectomy, or pelvic and/or para-aortic lymphadenectomy

Exclusion Criteria:

• those who refused to give consent
• inability to understand the research questionnaire
• severe psychiatric or mental disorders
• American Society of Anesthesiologists (ASA) physical status classification > III
• conversion to laparotomy.